What did physicists use to develop more powerful lasers?

A team of physicists has taken a step forward in creating more powerful lasers from sound, not light, opening the way to numerous practical applications beyond mere scientific fascination.

Traditional lasers are already impressive, having been developed relatively recently in the 1960s. “Lasers produce a narrow beam of light where all the light waves have very similar wavelengths. The laser waves travel together with the tips aligned, i.e. in phase. This is why laser beams are very narrow, very bright, and can be focused into an extremely small point,” explains NASA.

Although sound and light have essential differences (for example, sound only propagates through media such as fluids and solids), physicists are working to create sound-based lasers by manipulating phonons.

Contents hide

1 What are phonons?

2 Can we use sound to make lasers more powerful?

3 We recommend you also read:

3.1 About The Author

3.1.1 Janice Ewart

What are phonons?

“Just as photons make up beams of light, indivisible quantum particles called phonons make up a beam of sound. These particles arise from the collective motion of trillions of atoms, just as a ‘fan wave’ in a stadium is caused by the movement of thousands of spectators. When you listen to a song, you hear a stream of such small quantum particles,” explains Andrew N. Cleland, a professor at the University of Chicago Pritzker School of Molecular Engineering (USA), in a 2023 paper.

“Originally designed to explain the heat capacities of solids, phonons are predicted to obey the same quantum mechanical rules as photons. However, the technology for generating and detecting individual phonons has lagged behind that for photons,” continues the professor.

Can we use sound to make lasers more powerful?

In the new study, the scientists used a silicon oxide (SiO2) microsphere, which they suspended using light beams. It began to vibrate, producing an internal sound, like a high-frequency beep, but also sounds beyond the human hearing spectrum. The researchers then manipulated the microsphere using an alternating electric field to cause resonance, amplifying the sound waves up to a thousand times.

“By applying a monochrome electron injection to this levitated system, a huge amplification of the higher-order phonon harmonics can be achieved, with an enhanced brightness of more than 3 orders of magnitude and a reduced bandwidth of 5 orders of magnitude,” the team explains in the paper .

The experiment was conducted in a vacuum to better measure the sound waves trapped inside the microsphere, and the study is an important step toward creating more powerful sound-based lasers that can be used in fields ranging from ocean exploration and mapping through sound to to the advancement of medical imaging techniques.

“This study, which provides much stronger and better quality signals of coherent phonon harmonics, is a key step towards the control and use of nonlinear phonon lasers for applications such as phonon frequency combs, broadband phonon sensors and biomedical ultrasonic diagnostics,” concludes the chip, quoted by IFL Science.

The study was published in the journal eLight.